A person’s ABO blood type is determined by three alleles of gene I. If I A is pr

Question

A person’s ABO blood type is determined by three alleles of gene I. If IA is present, then the person will have the A antigen present on their red blood cells (RBCs). If IB is present, then the person will have the B antigen on their RBCs. The recessive allele (i) does not add an antigen to the RBCs. People who are homozygous recessive (ii) will have Type O blood. People who are homozygous for IA (IA IA) or heterozygous (IAi) will have type A blood. People who are homozygous for IB (IB IB) or heterozygous (IBi) will have type B blood. People who have one IA allele and one IB allele will have type AB blood.

The alleles of a second gene, gene H, also affect a person’s ABO blood type. People who are homozygous or heterozygous for the dominant allele of gene H (HH or Hh) will have the blood type that is determined by gene I. People who are homozygous recessive for gene h (hh), which is known as the Bombay Phenotype, will always have type O blood, regardless of which alleles they have for gene I because the h allele prevents the A or B antigens from being attached to RBCs.

1) The interaction between the alleles for gene I is an example of:

2) The interaction between gene H and gene I is an example of:

3) A father with the genotype Hh/ IA IB and a mother with the genotype Hh/ IBi have 3 children. What blood types (phenotypes) could not occur in the children based on the parents’ genotypes?

4) A father with the genotype hh/ IAIA and a mother with the genotype Hh/ IAIB have 3 children. What blood types (phenotypes) could not occur in the children based on the parents’ genotypes?

Explanation / Answer

1). b). Epistasis

If the phenotypic character expressed by one gene is influenced by another single or group of genes is known as “epistasis.” The given case(Bombay Phenotype) is an example of recessive epistasis.

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